The present invention relates generally to devices for measuring the volume of air flowing into or out of air conditioning systems. More specifically, the present invention relates to an improved device and method for measuring air volume flow over a wide range of flow capacities.
The use of air conditioning systems in both industrial and residential settings is widespread. An important consideration in the installation and operation of any air conditioning system whether it be a multi-story commercial building or a residential dwelling is providing the desired flow of air into the various rooms or areas within the building. It is, therefore, important that devices be provided which are capable of measuring the volume of air flowing into or out of the air conditioning ducts within the system. These devices are not only necessary during installation of the air conditioning systems to insure proper installation, but they are also necessary on a continuing basis for trouble-shooting and locating breakdowns in the air conditioning system where air flow through the ducts falls below desired levels.
Prior air flow measuring devices have been based upon the measurement of the velocity pressure of air going through a channel or duct of known cross-sectional area located within the device. The volume of air could then be calculated since the air flow in cubic feet per minute (CFM) is a function of the size of the channel through which the air is flowing and the velocity pressure (CFM=Velocity Pressure.times.Duct or Channel Cross-Sectional Area). In general, the prior devices include a manometer or other velocity pressure indicator which is calibrated with respect to the particular cross-sectional area of the channel or duct through the device so that air flow can be read directly from the manometer in CFM's.
Although the prior devices are well suited for measuring air flow through air conditioning ducts within certain restricted ranges. They are not well suited for measuring wide ranges of flow volumes due to the fixed cross-sectional area of the flow channel in the device. It would be desirable to provide an air flow measuring device which could be used for measuring the air flow through the air conditioning conduits or ducts of a wide range of air conditioning systems. For example, it would be desirable to have a device which could measure the relatively small air volumes typically passing through residential air conditioning systems with the same device also being capable of measuring the much greater air flow through commercial and industrial air conditioning systems.